Rectifiers are used to convert an alternating voltage into a direct-current voltage. Known rectifiers are usually installed in bridge circuits having multiple diodes as rectifier elements. Common designs are so-called half-bridge or full-bridge rectifiers. In addition, motor vehicle alternating current generators generally include a bridge rectifier for supplying the vehicle electrical system with direct-current voltage. The rectifier has a power loss which is specified by the resistance of the diodes and the output current. This power loss may be reduced only slightly by using circuitry measures such as connecting multiple diodes for each phase in parallel, for example. It is therefore known to replace the rectifier diodes with active switches, for example MOSFET transistors, via which the power loss may be significantly reduced. However, the use of active switches requires activation of the switches synchronously with the phase frequency. The point in time at which the switches are switched on and off is particularly critical. Activation of the switches with the aid of a control device is relatively complicated and imprecise in the case of the known rectifiers.